A wide variety of LED drivers or regulators are used in providing high power or high current levels to high brightness LEDs, on the order of 20-25 mA, and typically up to 1 A. For example, Supertex Inc. (HV9925 data sheet) and Melexis Microelectronic Integrated Systems (MLX10803 data sheet) provide peak current control with a constant off-time, but require external loop compensation and restrict the accuracy and dynamics of the converter. External loop compensation, requiring feedback through a current sense resistor which is used to measure the current through the LEDs, compromises the efficiency of the regulator. That decreased efficiency means excessive power consumption, which is highly detrimental for portable, battery-operated applications.
LED drivers generally have very low efficiency, making them highly unsuitable for applications in portable devices such as cameras and mobile telephones. These drivers generate a very high ratio of peak to average current for typical LED devices, leading to potential damage and reduced reliability. In addition, such drivers use analog current regulators, rather than digital, resulting in increased cost for the driver.
Accordingly, a need remains for a driver circuit or current regulator for solid state devices, such as LEDs used in lighting applications, which can provide digital control without requiring external compensation. Lastly, the current regulator should utilize comparatively few components, providing reduced cost and size, while simultaneously increasing its efficiency and enabling longer battery life when used in portable devices.